Welcome! Druidry and Left Hand Path, that is a very interesting combination. It can definitely work out, especially if you view the spirits you work with in a teacher and student or personal relationship among equals as opposed to master and slave. Definitely would be interested in how you incorporate it.
As far as how to prepare for spirit work, getting to know as much about the spirit is important to help get you in the mindset. Keep in mind that there is a lot of bias and dogma out there (especially if we are talking dark deities or the demonic) but the research helps to add power to your rituals. As far as approach, treat them like any other person you are just meeting. Treat them with respect and it will be returned.
I also recommend practicing mediation and developing your astral senses if you have not already. There are a few good tutorials on evocation and communicating with spirits in general. I’ll put a couple down below. And of course, ask questions and we will do what we can to answer.
^While they are geared towards demons, I can see them working just as well for gods with a bit of tweaking.
As far as the more druid end, I recommend the books Irish paganism by Morgan Daimler and The Apple Branch by Alexei Kondratiev. Welcome again!